While it is well known that all cells depend on metabolic energy to accumulate various nutrients, hardly anthing is known about the energy coupling mechanism. To elucidate the coupling mechanism at the molecular level it is necessary to identify and characterize the relevant membrane components, especially the protein components. For this purpose we are using a simple homofermentative microbe, Streptococcus faecalis as a model system. There is considerable evidence that the membrane ATPase in the organism is involved in the energized transport of K ions and amino acids. The major objective of the project is to fully characterize the ATPase and the membrane proteins with which the enzyme is associated. Certain ATPase-associated membrane components are known to exist. They are an attachment protein (nectin), the "carbodiimide sensitizing factor" and the trypsin-sensitive receptor site for the ATPase. To aid in identifying the carbodiimide sensitizingg factor we will make use of DCCD-resistant mutants of S. faecalis. The ATPase has been found to contain tightly bound ATP. We will attempt to elucidate the physiological significance of this ligand in the enzyme.